This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-000590, filed Jan. 6, 2000, the entire contents of which are incorporated herein by reference.
The present invention relates to a film forming apparatus and method for forming a TiN film, etc., by a CVD (Chemical Vapor Deposition) process using an ALD (Atomic Layer Deposition) method.
In a semiconductor device that should be miniaturized, use is made of a thin film of a metallic compound, such as tungsten silicide (Wsi), titanium nitride (TiN) or titanium silicide (TiSi), as a material for a connection line and barrier layer formed on a semiconductor wafer (hereinbelow referred to as a wafer) that is an object to be processed. The thin film of such metallic compounds is used as a buried layer formed as an interconnect line or a contact hole for interconnection between lines or in a groove, etc.
Conventionally, such a metal compound thin film has been formed by a physical vapor deposition (PVD) method such as the sputtering. With a recent trend toward a higher density integration and a resultant thinner and thinner interconnect line or film, as well as with recent stricter design rules in particular, however, the PVD method provides no adequate countermeasure because a film formed is poor in xe2x80x9cburyingxe2x80x9d property. For this reason, the CVD method has still been used by which a better xe2x80x9cburyingxe2x80x9d property and better film formation can be expected. However, the use of the CVD method provides no adequate countermeasure for film quality required, step coverage and intimate adhesion of a film. For example, Jpn. Pat. Appln. KOKAI Publication No. 55-130896 discloses the technique of forming a metallic compound thin film having a better quality and optimal adhesion and step coverage and an attention has been paid to the ALD method.
In order to deposit the metallic compound thin film, the CVD method using the ALD technique may be utilized. Stated in more detail, upon the formation of a TiN film for example, one wafer is loaded into a chamber, TiCl4 gas is supplied into the chamber, depositing a mono atomic layer of Ti layer. Then NH3 gas is supplied into the chamber, depositing a mono atomic layer as a nitride (N) layer doing so, these are reacted together in a heating atmosphere. By repeating such operation a predetermined number of times a TiN film of a predetermined thickness is obtained.
Upon the formation of a metallic compound thin film using the ALD technique, the switching of these supplying gases needs to be made at high speeds. A high-speed switching valve is used for this purpose. The high-speed switching valve has, however, a short service life.
Further, upon the formation of a plurality of mono atomic layers, a process gas for forming a first film is supplied and then a purge gas is supplied before the supplying of a process gas for forming the second layer. By doing so, the earlier supply gas needs to be completely exhausted from the chamber with the purge gas, thus taking a longer time in the formation of an intended film and hence lowering the productivity involved.
It is accordingly the object of the present invention to provide a film forming apparatus and method which can form films in high productivity with the use of an ALD method and can do so without using any high speed switching valve.
The present invention provides a film forming apparatus comprising: a chamber for holding substrates; a substrate holding section for holding these substrates within the chamber; first process gas discharge sections provided within the chamber and discharging a first process gas; second process gas discharge sections provided at those positions different from those of the first process gas discharge sections and discharging a second process gas; a rotation mechanism for rotating the substrate holding section and a heating section for heating the substrates. While the substrates are rotating as the substrate holding section rotates, films are formed on the substrates by alternately forming a mono atomic layer by the first process gas and a mono atomic layer by the second process gas over the substrates.
Further, the present invention provides a CVD film forming method for discharging first and second process gases from the first and second process gas discharge sections provided at mutually different positions onto corresponding substrates revolved within a chamber and forming films on the substrates by alternately forming a mono atomic layer by the first process gas and a mono atomic layer by the second process gas over the substrate.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.